Objective—To determine the minimal ultrasonic aspirator
pressure necessary to damage the cerebral cortex
of healthy dogs.
Animals—9 mixed-breed dogs.
Procedure—The study comprised 2 parts. In part A,
6 dogs were euthanatized immediately prior to the
experiment. In part B, 3 dogs were anesthetized for
recording of physiologic variables. In both parts,
craniectomy and durotomy were performed to bilaterally
expose the lateral aspect of the cerebral cortex.
An ultrasonic aspirator was placed in contact with various
areas of the cerebral cortex, and aspirator power
was altered (10, 20, 30, and 40%). Duration of contact
at each power was 5 and 10 seconds.
Subsequently, gross morphologic and histologic damage
was assessed in the cortex.
Results—Gross observations for all dogs were similar.
At 10% power, visible or histologic damage was
not evident in the cortex. At 20% power, the cortex
was slightly indented from contact with the hand
piece; however, cortical disruption was not evident.
Cortical disruption was initially detectable at 30%
power in some dogs and was consistently evident at
40% power in both sets of dogs.
Conclusions and Clinical Relevance—Ultrasonic
aspirator power of < 20% created minimal acute morphologic
damage to the cortex. Power settings
between 20 and 30% may superficially damage the
cerebral cortex in healthy dogs, whereas 40% power
consistently damages the cerebral cortex. Knowledge
of the degree of damage to cerebral cortex caused by
various amounts of power for ultrasonic aspirators
will allow surgeons to avoid damaging normal brain
tissues during surgery. (Am J Vet Res 2001;62:
Objective—To determine the change in stiffness as evaluated by the dorsal bending moment of cervical vertebral specimens obtained from canine cadavers after internally stabilizing the vertebral motion unit (VMU) of C4 and C5 with a traditional pin-polymethylmethacrylate (PMMA) fixation implant or a novel screw-bar–PMMA fixation implant.
Sample Population—12 vertebral column specimens (C3 through C6) obtained from canine cadavers.
Procedures—A dorsal bending moment was applied to the vertebral specimens before and after fixation of the VMU of C4 and C5 by use of a traditional pin-PMMA implant or a novel screw-bar–PMMA implant. Biomechanical data were collected and compared within a specimen (unaltered vs treated) and between treatment groups. Additionally, implant placement was evaluated after biomechanical testing to screen for penetration of the transverse foramen or vertebral canal by the pins or screws.
Results—Treated vertebral specimens were significantly stiffer than unaltered specimens. There was no significant difference in stiffness between vertebral specimen groups after treatment. None of the screws in the novel screw-bar–PMMA implant group penetrated the transverse foramen or vertebral canal, whereas there was mild to severe penetration for 22 of 24 (92%) pins in the traditional pin-PMMA implant group.
Conclusions and Clinical Relevance—Both fixation treatments altered the biomechanical properties of the cervical vertebral specimens as evaluated by the dorsal bending moment. There was reduced incidence of penetration of the transverse foramen or vertebral canal with the novel screw-bar–PMMA implant, compared with the incidence for the traditional pin-PMMA implant.